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'\" t
.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH strsep 3 2025-05-17 "Linux man-pages (unreleased)"
.SH NAME
strsep \- extract token from string
.SH LIBRARY
Standard C library
.RI ( libc ,\~ \-lc )
.SH SYNOPSIS
.nf
.B #include <string.h>
.P
.BI "char *strsep(char **restrict " stringp ", const char *restrict " delim );
.fi
.P
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.P
.BR strsep ():
.nf
Since glibc 2.19:
_DEFAULT_SOURCE
glibc 2.19 and earlier:
_BSD_SOURCE
.fi
.SH DESCRIPTION
If
.I *stringp
is NULL, the
.BR strsep ()
function returns NULL
and does nothing else.
Otherwise, this function finds the first token
in the string
.I *stringp
that is delimited by one of the bytes in the string
.IR delim .
This token is terminated by overwriting the delimiter
with a null byte (\[aq]\[rs]0\[aq]),
and
.I *stringp
is updated to point past the token.
In case no delimiter was found, the token is taken to be
the entire string
.IR *stringp ,
and
.I *stringp
is made NULL.
.SH RETURN VALUE
The
.BR strsep ()
function returns a pointer to the token,
that is, it returns the original value of
.IR *stringp .
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbx lb lb
l l l.
Interface Attribute Value
T{
.na
.nh
.BR strsep ()
T} Thread safety MT-Safe
.TE
.SH STANDARDS
BSD.
.SH HISTORY
4.4BSD.
.P
The
.BR strsep ()
function was introduced as a replacement for
.BR strtok (3),
since the latter cannot handle empty fields.
.SH CAVEATS
Be cautious when using this function.
If you do use it, note that:
.IP \[bu] 3
This function modifies its first argument.
.IP \[bu]
This function cannot be used on constant strings.
.IP \[bu]
The identity of the delimiting character is lost.
.SH EXAMPLES
The program below is a port of the one found in
.BR strtok (3),
which, however, doesn't discard multiple delimiters or empty tokens:
.P
.in +4n
.EX
.RB "$" " ./a.out \[aq]a/bbb///cc;xxx:yyy:\[aq] \[aq]:;\[aq] \[aq]/\[aq]"
1: a/bbb///cc
\-\-> a
\-\-> bbb
\-\->
\-\->
\-\-> cc
2: xxx
\-\-> xxx
3: yyy
\-\-> yyy
4:
\-\->
.EE
.in
.SS Program source
\&
.\" SRC BEGIN (strsep.c)
.EX
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
\&
int
main(int argc, char *argv[])
{
char *token, *subtoken;
\&
if (argc != 4) {
fprintf(stderr, "Usage: %s string delim subdelim\[rs]n", argv[0]);
exit(EXIT_FAILURE);
}
\&
for (unsigned int j = 1; (token = strsep(&argv[1], argv[2])); j++) {
printf("%u: %s\[rs]n", j, token);
\&
while ((subtoken = strsep(&token, argv[3])))
printf("\[rs]t \-\-> %s\[rs]n", subtoken);
}
\&
exit(EXIT_SUCCESS);
}
.EE
.\" SRC END
.SH SEE ALSO
.BR memchr (3),
.BR strchr (3),
.BR string (3),
.BR strpbrk (3),
.BR strspn (3),
.BR strstr (3),
.BR strtok (3)
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